Programmed Data Processor (PDP) was a series of minicomputers made and marketed by the Digital Equipment Corporation from 1957 to 1990. The name 'PDP' intentionally avoided the use of the term 'computer' because, at the time of the first PDPs, computers had a reputation of being large, complicated, and expensive machines, and the venture capitalists behind Digital (especially Georges Doriot) would not support Digital's attempting to build a "computer"; the word "minicomputer" had not yet been coined. So instead, Digital used their existing line of logic modules to build a Programmable Data Processor and aimed it at a market which could not afford the larger computers.
The various PDP machines can generally be grouped into families based on word length.
The PDP-12 Programmed Data Processor was a versatile digital computer which includes within its single central processor two distinct operating modes, each with its own complete instruction set. This versatility of the PDP-12 makes it, on the one hand, a laboratory-oriented machine with several built-in facilities for input/output, auxiliary storage, and control and sensing of external equipment, and, on the other hand, a general-purpose computer with a flexible input/output capability to which numerous peripheral devices may be easily attached. The central processor logic is fully parallel using a basic word length of 12 bits. The instruction cycle time is 1.6 microseconds; most instructions require from 1 to 3 cycles for execution.
Like its predecessor, the LINC-8, the PDP-12 operates in one mode as a LINC (Laboratory INstrument Computer), and in the other mode as a PDP-8 computer - specifically, a PDP-8/I. Unlike the LINC-8, however, the PDP-12 has one central processor and both operating modes have equal status. (In the LINC-8, the LINC mode was subordinate to the PDP-8 mode). The computer may be stopped and started in either mode, and programs may switch from one to the other at will. Computations in one mode are immediately available to programs operating in the other mode because only one set of processing registers is involved.
The PDP-l2 is offered in three configurations: A, B, and C in order of decreasing capacity. The two smaller systems, B and C, are expandable into the A configuration. The system discussed in this handbook is the PDP-12A.
The basic memory capacity of the PDP-12 is 4096 (4K) 12-bit words and can be expanded to 32,768 (32K) words of core storage.
Browsing the Collection
There are 62 images for the DEC PDP-12, all collections.